CNT have a specific configuration of having an outside surface formed of graphene, and therefore application in various fields is expected as a functional material and also as a structural material. Specifically, CNT have excellent characteristics, such as high mechanical strength, light weight, satisfactory electrical conduction characteristics, satisfactory heat characteristics such as heat resistance and heat conductivity, high resistance to chemical corrosion, and satisfactory field emission characteristics. Accordingly, the use of CNT conceivably includes a lightweight and high strength wire, a probe of a scanning probe microscope (SPM), a cold cathode of a field emission display (FED), an electrically conductive resin, a high strength resin, a corrosion-resistant resin, a wear-resistant resin, a highly lubricating resin, electrodes of a secondary battery and fuel cell, an interlayer wiring material for LSI, and a biosensor.
As one of production methods for CNT, Patent Literature No. 1 discloses a method comprising: preliminarily forming a solid-phase metal catalyst layer on a surface of a substrate by means of sputtering and the like, such as by vapor-depositing a thin film of a metallic material; disposing the substrate provided with the solid-phase metal catalyst layer in a reactor; forming catalyst particles from the metal catalyst layer to be growth nuclei on the substrate; and feeding a hydrocarbon gas into the reactor to form a CNT array on the substrate. Hereinafter, the method comprising: forming the solid-phase catalyst particles as the growth nuclei on the substrate as described above; and feeding a hydrocarbon-based material into the reactor, in which the substrate provided with the solid-phase catalyst particles is disposed, to produce a CNT array will be referred to as a solid-phase catalysis process.
As a method for highly efficiently producing a CNT array by the solid-phase catalysis process, Patent Literature No. 2 discloses a method of feeding a material gas that contains carbon and no oxygen, a catalyst activator that contains oxygen, and an atmospheric gas, while meeting predetermined conditions so that they are brought into contact with a solid-phase catalyst layer.
Another method is also disclosed which produces a CNT array in a different manner from that of the method described above. More specifically, Patent Literature No. 3 discloses a method comprising: sublimating iron chloride; using the sublimated iron chloride as a precursor to form a catalyst to be growth nuclei on a substrate; and using the catalyst to form a CNT array. This method is substantially different from the arts as disclosed in Patent Literature Nos. 1 and 2 in that a halogen-containing substance in gas-phase is used as a catalyst precursor and this substance is used to form a catalyst. In the present description, the production method for a CNT array as disclosed in Patent Literature No. 3 will also be referred to as a gas-phase catalysis process.